Products which are made of many different parts and subassemblies, such as automobiles, trucks, boats, airplanes, etc. are typically built and assembled in a factory using mass-production assembly techniques. In order to produce a large volume of items, the amount of each type of part which is required for each item must be determined. When only one product design is permitted, the material production requirements can be determined simply by multiplying the requirements for one item by the number of items to be produced. However, when the product to be produced is available in a variety of designs, each of which has different parts, determining the production requirements for a set of product orders becomes more difficult. This is particularly true for products, such as automobiles, which have a large number of parts, are produced in high volumes, and are often marketed with a large variety of different features and options that must be installed at the factory, such as engine type, transmission, and the like.
A manufacturing resource planning (“MRP”) system is used to process and track information related to manufacturing, marketing, costs, part and spare part requirements, and other aspects of the production, sale, and maintenance of an article. In a conventional MRP system of the tape used in the mass production of automobiles, the parts requirements of a standard version of the product are detailed in a list or table called a bill of materials (“BOM”). To introduce each new design variation (e.g. an automatic transmission instead of a standard transmission), an auxiliary BOM is generated which details the parts which must be added to the standard BOM to produce the variation, as well as the parts which must be removed from the standard BOM. Because design variations selected in combination may affect the parts requirements in ways which differ from inclusion of the variations separately, additional auxiliary BOMs are also often required to adjust the original and adjusted part requirements.
To calculate the manufacturing parts requirements for a car produced with the new option, the parts requirements specified in the standard BOM and one or more auxiliary BOMs are combined using an add-subtract process wherein the parts detailed in the appropriate auxiliary BOMs are added to and subtracted from the part requirements detailed in the standard BOM. Logical rules which can be evaluated in accordance with customer order options are defined and are used to select which of the many auxiliary BOMs should be combined with the primary BOM for a particular customer order. While effective for designs with a small number of options, when more than a small number of design variations are available, the various BOMs and associated documentation quickly become very complex and difficult to process.
In an alternative representation, every part used in all of the defined variants is included in a single BOM. Each part has an associated construction code rule which indicates when the part should be included. The construction code rules for all valid design variations are typically defined at the same time. The code rules which are entered can be very complicated because they must be defined in such a way that code rules for alternate variations do not “overlap” each other or have other logical ambiguities or inconsistencies.
The difficulty of defining code rules is further complicated when new design variants are added after the initial design is defined because a given code rule for one particular variation can be dependent on which other variations are permitted. In addition to defining a new code rule when a new design variation is added, one or more other, previously generated rules may also need to be updated. This can be a complex and error-prone task because conventional systems do not provide an easy mechanism to identify which code rules may be affected.
In addition to defining one or more BOMs, extensive design documentation must be prepared. Documentation is necessary both for making decisions about the cost, production and delivery time, capacity restrictions, connecting processes. etc. which result from including a variant in the customized product, and also to ensure that information about all the parts used in each product produced is available for historic analysis—i.e. for recalls, analysis in the event of product failure, etc. Conventional systems document each module or subassembly variant from the “top-down”, wherein all possible combinations of variants are separately documented. For example, a car design may include a seat assembly which can have one of three types of material (e.g., cloth, leather, vinyl), two adjustment mechanisms (manual or power), and two heat options (none, or heated seat). There are therefore 3*2*2=12 possible combinations of seat assemblies. In the conventional top-down design method, each of the twelve seat assembly variants is documented separately.
It is apparent that as the number of design variants increases, the amount of documentation required increases exponentially. When product assemblies have a large number of options, it becomes practically impossible to document every variant. In a particular truck design, for example, the total number of possible wiring harness configurations (which depends on a large number of factors, including not only the electronic components used, but also the relative position of the components) can be on the order of 263 (about 1019). Because it is practically impossible to document every design variation, a manufacturer must predict which design variations or combinations of options are likely to be the most popular with customers, document only those variations, and then prevent the customer from ordering other non-documented option combinations. This prediction can be both under inclusive, omitting options which may be popular with customers, and over inclusive, including options which are at best, only infrequently ordered.
In addition to the difficulties associated with defining code rules and documenting numerous design variations, a further drawback to conventional MRP systems is the time required to analyze customer orders and to generate information about what parts are required to manufacture the set of orders, when they are needed, and where the parts must be on the assembly line. Conventional systems determine part totals by evaluating, for each customer order, every code rule in the BOM. When a “hit” occurs (i.e., an evaluated code rule is true and thus the part will be used), a data item is written to an output record in a computer data file. This process is repeated for every customer order being considered.
A typical BOM for a luxury automobile can include 70,000 separate part/rule entries. Each part entry has an associated code rule which must be evaluated to determine whether the part should be included in a given build according to the selected customer options. In a typical example, about 4000 particular rules are likely to be true for a given customer order and processing a single order may take up to several minutes. Thus, for a production run of 8000 cars, it is not unusual for the MRP process to take a considerable amount of time to process and to result in a parts requirement file on the order of 10 gigabytes in size, which file does not include process information. Even if the MRP system utilizes parallel processing to evaluate multiple customer orders simultaneously, the process can still take several hours to complete. Because of the file size and duration of the process, conventional MRP systems are operated as batch routines. In addition, the long time needed for the analysis prevents production line managers and others from making rapid changes in the sequence customer orders are filled, because the effect of those changes cannot be calculated quickly enough.
Since many factories now operate on the “just-in-time” and “real-time” principles, where parts required for production are delivered to the factory shortly before or as they are needed, the slowness of current MRP systems can have a significant impact on a factory's profitability. If the production line cannot respond quickly to temporary shortages in parts or delayed deliveries, the resultant slow-downs or shut-down of the production line can directly affect the profitability of the factory.
Accordingly, it is an object of the invention to provide a process for defining and managing the part, part variant, part connection, and part connection variant details related to the manufacture of an article in a simple and compact manner.
It is a further object of the invention to provide a process for use in preparing a BOM which fully describes the part requirements for all variants of a given product design while avoiding the exponential growth of auxiliary BOMs and variant documentation as new design variants are introduced.
Another object of the invention is to provide a method and system for more quickly evaluating the code rules in a BOM to determine the manufacturing parts requirements and other information in accordance with one or more customer orders.
Yet a further object of the invention is to provide a resource and requirement planning system and method in which process and activity data relating to the physical and/or functional connections between parts can be tracked.